(1) Field of the Invention
The present invention relates to the control of alternating current powered appliances and particularly to the exercise of control over electric lamps. More specifically, the present invention is directed to time delay circuits for discontinuing the delivery of alternating current to electrically energized devices through stepwise reductions in power. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in the control of alternating current energized electric lamps. There are innumerable situations wherein it is necessary or desirable to take steps to extinguish a lamp while insuring that the area in which the lamp is situated will remain illuminated for a sufficient period to permit safe egress therefrom. In the past this has been accomplished through the use of conventional time delay switches either built into the lamp or otherwise connected in the circuit through which power is supplied to the lamp.
The use of conventional time delay switches has failed to recognize and/or solve a physiological problem associated with the automatic extinguishing of lamps subsequent to the departure from the vicinity of the lamp of the individual commanding the extinguishing action. Thus, existing lighting devices with delayed extinction abruptly plunge the room or other area into darkness at the end of the normal time delay period and it is extremely difficult to gauge the time remaining before the end of the temporary delay period. This inability to accurately gauge the time remaining before illumination ceases results either in undue haste, with the inherent potential for accident, or may leave the individual "stranded" in the dark.
The above-discussed problem, incident to the inability to accurately measure the time remaining before interruption of power to a lamp equipped with a time delay switch, has previously been solved by resort to a multiplicity of switches. Thus, in commercial and residential wiring, it is common practice to provide switches adjacent each exit doorway; there typically being as many switches as there are lamps in the room which one desires to individually control. This multiplicity of switches results in substantial added expense.